How to Manage Coordination Between Facade Contractors and Structural Engineers on Large-Scale Projects
Most coordination problems on facades are actually procurement problems, masquerading as communication challenges. Take a fight between a facade contractor and the structural engineer on site, or a shop drawing that’s returned for the third time for the same issue - the root cause is rarely a communication breakdown. Often it is a decision made months earlier to defer responsibility for the facade specification to “later in design.” By the time “later in design” rolls around, the structural engineer has already made assumptions about the loads, spans, and connections that might apply to a generic building.
These are not procurement problems: they are procurement problems wearing a technical disguise.
Structural engineers calculate column sizes, slab edges, and connection details based on the loads they’re told to design for. If those are allowances (wind pressures, bracket spacing, approximate dead load per square meter), there’s no greater accuracy in an engineer’s calculations than in the numbers they’re given. This is why value engineering after structural drawings have been issued can be so costly: choosing a different panel type changes the panel weight, the bracket spacing, the bracket reactions, and the loads on connections, potentially requiring rework to connections that had already been built or detailed.
It is why coordination is fundamentally a collaboration issue between these design teams: two groups can communicate as much as they want, but if one makes critical decisions about the design of another long after the design has already been issued, they are going to clash downstream, despite the communication.
The easiest way to avoid clashes is to decide on a facade type early enough that changes to it don’t require changes to other disciplines’ work
Which brings us to…
Bring the facade contractor in as a design-assist partner, not a bidder.
On most projects, especially large commercial ones, the facade takes the form of a separate procurement package, bid by a specialty contractor as a downstream trade. This inevitably creates a design conflict, because it puts the contractor in the position of having to coordinate a complex design to the structural framing after the framing has already been designed.
A better option is design-assist procurement: bringing in the contractor earlier, to help with design development, before the point where it would be too late to change the framing in response to the loads, brackets, and panel weights the selected facade would require.
That’s how you prevent downstream RFIs: you simply stop guessing about the relationship between the two sets of drawings, and design everything to the same set of requirements.
Design-assist is slightly more expensive, but far less costly than the change orders that often result when a steel structure has to be modified months after its construction, because the value-engineered change to the facade turned out to have unacceptable loads.
The tolerance conflict nobody puts in the contract
Steel structures are typically constructed to tolerances of one or even two centimeters, while cladding and curtain wall systems often need to be installed to tolerances of one millimeter or less, at the edge of each panel, to prevent visual distortions or gasket leaks. This discrepancy has to be resolved somewhere, and it typically takes the form of scope creep, unless it’s been clearly defined in detail prior to the start of either discipline’s work.
Too often, this is not done. The structural scope might state that structures are to be erected to standard tolerances, while the facade scope might specify plumb and level installation of cladding within manufacturer tolerances. But neither will necessarily state who is responsible for reconciling the difference between the two sets of tolerances, or designing connections that can absorb it, leaving this detail to be discovered on site - and remedied through a change order, if the discrepancy turns out to be significant. The reality is that some systems - brackets, anchors, or slots - absorb this discrepancy by design, and that detail needs to be designed and specified ahead of time, rather than left unspecified.
It’s better practice to explicitly state these tolerances in both scopes, along with a range of compensating adjustments and slotted connections, and have the anchor system designed for a certain maximum deviation.
A BIM protocol that actually catches clashes before fabrication
3D modeling is the one thing most projects already do, and it works brilliantly - unless someone forgets to check for clashes during design development, or simply doesn’t know who is responsible for actually resolving them.
A good BIM protocol has a collision-checking milestone at the end of design development, at LOD 350, when both disciplines have modeled their systems with sufficient detail for collision-checking. A second, stricter check happens later, at LOD 400, when shop drawings start being produced and the actual bracket connections can be checked against the model.
This is important, because the person who “finds” a clash in BIM (and therefore has responsibility to resolve it) is often the person who simply sees it first, rather than the person who should have known to avoid it in the first place.
Having explicit responsibility to resolve clashes at a certain point in the shop-drawing process ensures everyone has a deadline to do so, rather than an ongoing obligation to do so, especially if the person responsible has other duties.
Design connection forces for every bracket, not a uniform pressure
The structural engineer designing connections for a building’s facade should not design to a uniform pressure across the face of the building - that’s a design for a generic building. They should design to actual connection forces, after considering the panel size, joint spacing, and relationship to parapets, corners and other pressure-damping features that affect wind loads on individual brackets.
That means establishing the facade layout and bracket spacing early enough in the project for the structural connections to be designed to those assumptions, rather than changed later. The structural tender should not happen until the facade grid has been established, to avoid questions about bracket reactions and connection design on the part of the structural subcontractor after the fact.
It’s a question of risk management and value engineering: locking in on the building’s facade layout early ensures the engineer designing connections knows what they’re designing connections for.
This dovetails with our next point about long-lead procurement:
Long lead-time procurement informs connection design, and should be on the project risk register.
Imported aluminium cladding panels and high-performance glazing units often have lead times of many months, and are frequently the last items to be selected on a project, despite needing to be ordered months in advance of installation. By contrast, the structural connections for aluminium cladding panels need to be specified early, so that their weight can be incorporated into the structural calculations. A better practice is to make aluminium cladding panel selection early enough in the project for the structural engineer to size connection details based on their actual weight and reaction, and long enough in advance of installation to ensure any required lead time is properly noted on the project’s risk register.
Thermal movement and structural deflection define the joint type, not just the schedule
Aluminium framing typically moves at a different rate than steel or concrete superstructures. Wind sway, seismic movement, and deflection of concrete floors and slab edges under load can also affect the spacing of panels and brackets. This means the type of connection - rigid or sliding, two-way or one-way adjustable - and the adjustment range of the brackets need to be specified based on anticipated movement, not just temperature differentials.
The structural engineer needs to advise the facade contractor on the amount of sway and deflection at each story and connection for anticipated wind and seismic loads, as well as the deflection at slab edges, to help them select the joint type and anchor details. This information needs to be shared early enough to affect system selection, rather than just documenting the situation once a system has been chosen.
Set a hard RFI turnaround, because slow answers stall two schedules at once
RFIs for the interface between the structure and the facade are some of the most schedule-critical RFIs on a project, because a single unanswered question can stop both shop drawing production and panel fabrication at once. The standard 10 or 14 day RFI turnaround across most firms is too slow for an interface that is this schedule-critical, especially near the end of the project when panels are typically fabricated in parallel with other trades.
A good project-specific protocol sets a 72 hour maximum turnaround for RFIs from the facade to the structure, plus a specific structural reviewer for those RFIs, rather than a general one. This isn’t about expediting the review, per se - it’s about recognizing the unique sensitivity of a facade interface to delays in the process. The schedule impact of a two week delay on an early RFI can easily become a two-month delay later in the project, once you factor in the slowdown to shop drawing production, fabrication lead times, and the current status of the project’s critical path.
Assign slab edge weathertightness explicitly, or it becomes nobody’s responsibility
The connection between the facade and the slab edge is a frequent source of leaks, and one where the responsibility for watertightness and weatherproofing can be very difficult to identify. The cladding contractor’s scope of work rarely extends to the slab edge, and the structural connections to the building frame are rarely specified by the facade contractor, leaving the question of who is responsible for the watertightness of the transition between the two open.
That needs to change. The question of slab edge weathertightness needs to have an explicit owner at the contract stage, to avoid later disagreements about who is responsible for a leak. Watertightness of the system at the slab edge should be assigned to either the cladding contractor or a separate waterproofing subcontractor, rather than left to whoever is responsible for installing the slab or cladding membranes. The same applies to the interface detail itself: whoever is responsible for the weathertightness of the connection should have ownership over its detail and therefore design responsibility for it, including the selection of materials, flashing, and drainage. Disputes over who is responsible for a leak are far more likely to happen when the responsibility isn’t spelled out in detail in the contract, especially when each side cites their own drawings showing the leak as being outside their scope of work.
The math speaks for itself
According to the Construction Industry Institute, rework accounts for approximately 5 percent of construction costs, with a significant proportion of that related to interface issues between different systems, such as structural and envelope systems. This aligns with most project director’s anecdotal evidence about the costs of rework - rework identified in time to make changes to the design model is roughly equivalent to the cost of making those changes to the model; rework identified late in the process or after the fact typically involves field adjustments, impacting the schedule and often resulting in a contentious change order negotiation regarding who bears the cost of the rework.
Late rework is similarly expensive in terms of project scheduling, as rework to a project’s schedule-critical path often has a disproportionate impact on the overall project schedule. For instance, a two-week delay in a critical path activity can often result in a significantly longer delay to the overall project completion if that activity is a major constraint in the scheduling process. A similar delay to a project’s critical path activity can trigger knock-on disruption elsewhere, particularly if it necessitates extensive rework to other project activities.
The most effective way to avoid both kinds of rework is a risk management discussion with a façade contractor early in the design process.
As most project directors know, façade systems, particularly imported aluminium cladding systems and long-lead glazing, are typically the last major decision to be made by a design team, and the first major system to be installed by a specialty subcontractor. The resulting risk to the construction schedule and critical path can be considerable, and it deserves as much scrutiny as any risk to the project’s schedule during the design process. In short, risk management should be applied to the procurement of a building’s facade in the same way it is to any other design element or construction method that could cause schedule delays.
